Manchester City's Italian international striker Mario Balotelli has been ruled out for a month with a knee injury.

The 20-year-old has already missed a large chunk of the season after knee surgery and a suspension.

"I'm worried because he can't play for another three or four weeks at an important moment for us," said City manager Roberto Mancini.

"To have an operation done and then to have another problem two months later is strange," added Mancini.

"He may need surgery. We just don't know. He must rest, then he will have treatment and work. Hopefully then he will be OK."

Earlier this season Balotelli missed two months of the campaign after undergoing knee surgery in September and was quickly sidelined again through suspension after collecting a red card at West Brom.

The Italian's latest injury setback came on the day City unveiled new £27m signing Edin Dzeko, who will provide Mancini with an immediate striking option in the Italian's absence.

However Balotelli's knee problems may persuade City to keep Emmanuel Adebayor, who has been linked with a move away from Eastlands during the January transfer window, as has Paraguay striker Roque Santa Cruz.

"For Roque it is possible," said Mancini. "He is a good guy and he deserves to play. But with Emmanuel I don't know. We must wait and see."